Beliefs:
	/* The agent will strongly prefer to operate only in the higher floors.
	   Random part is added to decide ties automatically.
	 */
	cost(_, NewStop, up, Cost) :- NewStop >= 5, 
	                              Cost is (0 + rand).
	
	cost(_, _, _, Cost) :-     Cost is (10 + rand).                                  
	                                       
